A cube 7-compound can be constructed by combining a cube 6-compound with the original cube used to generate it.
It is implemented in the Wolfram Language as PolyhedronData["CubeSevenCompound", 1].
The cube 7-compound is illustrated above together with its octahedron 7-compound dual and common midsphere.
The common solid and the convex hull are unnamed solids illustrated above.